In modernized GNSS, some systems use long codes. For example, Galileo system uses a code with a length of 4 ms, which is four times of that of GPS L1C, in which the code length is 1 ms.
To acquire a satellite, a receiver must correlate a received signal with a full code. In Galileo, the full code has the length of 4 ms as mentioned above, that is, 4092 chips. Accordingly, the acquisition time is long, thereby negatively influencing the time-to-first-fix (TTFF), which is an important index for the receiver performance.